1. Technical Field
The present invention relates to an optical subassembly and, more particularly, to an optical subassembly which provides alignment between an active optical device and associated optical elements.
2. Description of the Prior Art
In the realm of optical device packaging, there is beginning to develop a number of assemblies which utilize a single crystal semiconductor material (such as silicon) as the support structure for the various optical devices. Often referred to as "silicon optical bench" technology, the utilization of silicon may result in a significant cost saving in optical packaging over some of the more esoteric materials which have been used in the past. More importantly, silicon processing technology has advanced to the stage where a number of relatively standard procedures (e.g., oxidation, metallization, etching--isotropic or anisotropic) may be utilized to facilitate attachment of the devices to the support member, as well as alignment therebetween. Further, it is possible to form optical waveguiding structures directly in/on a silicon substrate, resulting in the ability to form a completely operable optical subassembly in silicon.
An exemplary utilization of silicon in the formation of a subassembly for optoelectronic devices is disclosed in U.S. Pat. No. 4,945,400 (Blonder et al.) issued Jul. 31, 1990 and assigned to the assignee of record in this application. In general, Blonder et al. disclose a subassembly including a semiconductor (e.g., silicon) base and lid including a variety of etched features (e.g., grooves, cavities, alignment detents) and metallization patterns (e.g., contacts, reflectors) which enable the optoelectronic device to be reliably and inexpensively mounted on the base and coupled to a communicating optical fiber. In particular, Blonder et al. disclose an arrangement wherein the optoelectronic device (e.g., LED) is disposed within a cavity formed by a lid member and the communicating fiber is positioned along a groove formed in a base member. A reflective metallization is utilized to optically couple the device to the fiber. Therefore, positioning of the device over the reflector is the only active alignment step required to provide coupling. Any remaining alignments are accomplished utilizing fiducial features formed in the base and lid members.
Although the Blonder et al. subassembly represents a significant advance in the field of silicon optical bench packaging, a need remains for providing an arrangement which does not require active alignments. In particular, the provision of a completely passive optical packaging arrangement is considered both more reliable and less expensive than virtually any alternative requiring active alignment between components.